Vertex and Index buffers are handles to resources that youve have sent or intend to send to the GPU. The VB/IB structures are not expensive resources in themselves but if neccessary you can create and dispose them as you need. Generally you have one or many VB/IBs per model, rather than attempting to reuse them.

In that sense they are similar to programming in IO streams (in fact if they were called VertexStream and IndexStream you might get a better analogy - although its not perfect). Like IO stream programming, once youve committed data into a stream you rarely modify the contents, as you have explicitly "shared" the contents between other holders of the stream pointer - in this case the GPU. You can modified the contents of the VB/IB but its only done in specific circumstances for specific effects.

If you attempt to channel all your data per frame through one VB/IB you are preventing the GPU from seeing the "whole picture" and force it to process your draw call serially rather than use the parallelism that they specialise in.

Thank you very much. My approach will be as you say and suggest. I think it will be easier code to manage with each VB/IB / model.
I have found this example and this is exactly how i will structure my Models.
The Model itself will have their own VB/IB and fill them up and then on Render, you set this VB/IB to active before you render.

Mh, I'm very worried about what you're doing here.Besides the obvious syntactic errors which we skip over, a thing like

DrawPrimitives(triangle->count);

means little... or maybe it means something very different from what it suggests.

1st: I don't see how Model triangle; triangle.init(); could reasonably fetch itself with useful data. Which is the whole point of your question if you think at it!2nd: IBs or VBs don't draw. DrawPrimitives draws by using its parameters. So we have to store those parameters somewhere and your code suggests triangle->count must be a vector of DrawCallParameters or something. That's not good naming, or perhaps you should just try harder when writing examples.3rd: SetActiveBuffer can be much more involved than that (buffer offsets anyone?).4th: I sincerely hope you don't plan to use the same DrawPrimitive to render the whole level.

there is nothing OO in the code you are posting. You are not hiding data away, it's like C code, you are just using what I'd describe as "brute force" approach... a "render" function in a OO typical approach will be a single call to:

renderer->render( rootNode );

Which will just do something like rootNode->render(...) and then call render for all the children of the current node.
Typically every Node has a "render" function to render itself that hides away all the low level DX code.
This has been the approach for the last 10 years, nowadays things are changing into more data oriented way which doesn't map that well into OOP, but I'd still look into scene graphs trying not to get overboard with those.